The present invention relates to panels of composite material, in particular thermosetting or thermoplastic matrices, particularly for streamlined bodies, hatches, aircraft access doors and more particularly to panels with edges and/or external surfaces protected against shocks or erosion.
Such panels are exposed by their external surface to various aggressions such as particularly erosion due to air, water, sand, etc . . . or to shocks due to handling or to contact with unexpected objects such as birds, or to other causes, which can harm the integrity of the composite material and particularly give rise to separation of the fibers, particularly of carbon, imperiling the reliability of the structure.
The invention aims precisely at protecting the exposed surface and/or edges of such panels.
In the past, it has already been sought to protect edges of structures of streamlined bodies particularly exposed either to erosion phenomena or to shocks, and to this end, various known techniques for protection have been or could be used.
One means could consist in providing a cemented on metallic corner, of stainless steel or aluminum for example, of U-shape or L-shape, on one of the section or sections of the panel to be protected.
This technique, in the case of a panel of composite material, is difficult to use, particularly on shaped pieces, because of the monolithic character of the corner and of their nature. A stainless steel corner has in effect a hard and smooth surface condition preventing any structural adhesion of the cement, so that a very complicated chemical treatment is necessary, whilst an aluminum corner has the very high risk of corrosion, in the case of composite structures using carbon fibers, because of the existence of a very substantial aluminum-carbon galvanic couple.
Another solution consists in riveting a corner of stainless steel of U-shape or L-shape on the edge of the panel, but it is complicated and costly to use and requires precautions to preserve the metallization.
According to another solution described in U.S. Pat. No. 5,486,096 seeking to protect a wing profile of composite material, the leading edge of the structure is covered with a cap forming a grill of stainless steel shaped in correspondence to the attack edge to be protected.
Moreover, in GB 1 274 871, EP 0 730 951 and U.S. Pat. No. 5,315,820, there are disclosed panels of composite structure covered on one of the surfaces with a protective cladding including a metallic cloth, but such protection does not extend to the edges nor to the rim nor to the opposite surface of these panels.
The edge of a panel of composite material can also be covered with anti-erosion paint, but this solution is fragile and has low durability with time and requires replacement of the protection in the course of the surface lifetime of the structure. Moreover, it insufficiently protects the edge in particular in case of shocks during handling of the panel, in the case of the panel of doors and hatches, during cycles of opening/closing.
Moreover, such paint is badly adapted to sharp angles and it is often found, after drying the paint, that the edge is uncovered.
Finally, the use of paint is sensitive and the drying time is too long, of the order of a week for total drying.
A strip of polyurethane can also be envisaged for covering the edges of panels, but this material has too high a sensitivity to aeronautical liquids.
The covering of such edges can finally be carried out by spraying a layer of lacquer, but this solution is fragile and is not adapted to pieces that have to be frequently handled, such as hatches over motors.
The present invention seeks to overcome the various drawbacks of such solutions by providing other means, adapted to ensure protection that will be effective, durable and easy to use.
To this end, the invention has for its object a panel of composite material, in particular a thermosetting or thermoplastic matrix, with edges and/or an external surface protected from shocks or erosion, for all elements of streamlined compartments or nacelles of aircraft motors, characterized in that it comprises, over all or a portion of its edges, a cladding which forms a border overlapping the two opposite surfaces of the panel, constituted by a metallic cloth connected to the structure of the panel by means of an adhesive agent to fuse through said cloth.
According to one embodiment, said cladding covers all the external surface of the panel, as well as the edge and is prolonged along the edge of an internal surface of the panel.
In the structure according to the invention, the adherence of the metallic cloth to the panel structure, constituted by mineral fibers, particularly carbon plies, embedded in a matrix of suitable resin, is imparted by the resin impregnating the fibers or by a suitable adhesive or cement, the adhesive agent being diffused through the cloth.
The metallic cloth is for example constituted by a single layer structure of woven monofilaments of stainless steel.
Such panels are remarkable in that they have perfect integration of the protection to the structure of the panels thanks to the homogeneous connection between the protective metallic cloth and the composite material, provided by the intimate diffusion through the woven structure of the adhesive agent, namely the resin impregnating the fibers of the composite and/or the adhesive or cement that may be used.
The cementing of the protection is hence excellent and the nature of the protection, a metallic cloth perfectly applied against the composite, ensures excellent resistance to erosion and to chocks.